G70.81
BillableLambert-Eaton syndrome in disease classified elsewhere
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is G70.81 an HCC code?
Yes. G70.81 maps to Myasthenia Gravis/Myoneural Conditions and Guillain-Barre under the CMS-HCC V28 risk adjustment model (and Myasthenia Gravis/Myoneural Conditions and Guillain-Barre Syndrome under V24).
HCC Category Mapping
RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.
MEAT Criteria for G70.81
For G70.81 to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically — it has to be re-documented and supported each calendar year.
- MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
- EEvaluate: test results, medication response, or physical findings reviewed by the provider
- AAssess: explicit mention in the assessment or plan with acknowledgment of status
- TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis
Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed G70.81 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
G70.81 is the ICD-10-CM diagnosis code for lambert-eaton syndrome in disease classified elsewhere. Lambert-Eaton syndrome occurring as a complication of another disease, most commonly small cell lung cancer or other malignancies. G70.81 sits in the ICD-10-CM chapter for diseases of the nervous system (g00-g99), within the section covering diseases of myoneural junction and muscle (g70-g73).
Under the CMS-HCC V28 risk adjustment model, G70.81 maps to Myasthenia Gravis/Myoneural Conditions and Guillain-Barre (HCC 196) with a community, non-dual, aged base RAF weight of 0.402. Under the older CMS-HCC V24 model, G70.81 maps to Myasthenia Gravis/Myoneural Conditions and Guillain-Barre Syndrome (HCC 75) with a community, non-dual, aged base RAF weight of 0.425. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.
This code requires documentation of the underlying disease; code the associated condition separately. Because G70.81 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for G70.81 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This code requires documentation of the underlying disease; code the associated condition separately
- •Commonly associated with malignant neoplasms; ensure both conditions are coded
Clinical Significance
Lambert-Eaton syndrome in disease classified elsewhere is a manifestation code indicating that the neuromuscular disorder is secondary to another classified condition, most commonly malignancy. Capturing both the Lambert-Eaton syndrome and its underlying cause provides a comprehensive picture of the patient's disease burden and care requirements. This dual-code situation often yields substantial combined RAF impact.
Documentation Requirements
- ✓Documentation of the underlying disease causing the Lambert-Eaton syndrome
- ✓The underlying disease code must be sequenced first (etiology-manifestation convention)
- ✓Clinical features of Lambert-Eaton syndrome: proximal weakness, autonomic dysfunction
- ✓Electrodiagnostic or antibody testing confirming Lambert-Eaton syndrome
- ✓Treatment plan addressing both the underlying disease and the Lambert-Eaton syndrome
- ✓Provider's explicit documentation linking the Lambert-Eaton syndrome to the underlying condition
Excludes 1 — Do NOT code together
- Lambert-Eaton syndrome in neoplastic disease (G73.1)
Code First
- underlying disease